1. Technical Field
The present invention relates to a method for manufacturing a hydrogen-containing gas, comprising a mixing step of mixing, in a mixing chamber, an oxygen-containing gas with a feed gas obtained by mixing steam with a hydrocarbon fuel, and a reformation step of guiding the mixed gas obtained in the mixing chamber into a catalytic reaction chamber via an antechamber provided on the upstream side of the catalytic reaction chamber, and bringing the mixed gas into contact with a reforming catalyst and thereby obtaining a hydrogen-containing gas by means of a partial oxidation reaction and a steam reforming reaction, and relates to a manufacturing apparatus that makes use of this kind of method for manufacturing a hydrogen-containing gas.
2. Background Art
A hydrogen-rich gas can be obtained by utilizing a catalytic reaction to reform a hydrocarbon fuel as a feed gas for FT (Fischer-Tropsch) synthesis, methanol synthesis, or ammonia synthesis, for example. Partial oxidation reactions and steam reforming reactions are known as catalytic reformation reactions of this kind for hydrocarbon fuels. The above-mentioned partial oxidation reaction proceeds according to the chemical formula given as Chemical Formula 1 below, and is what is known as an exothermic reaction.CnH2n+2+0.5nO2→(n+1)H2+nCO (exothermic reaction)  [Chemical Formula 1]
The above-mentioned steam reforming reaction proceeds according to the chemical formula given as Chemical Formula 2 below, and is what is known as an endothermic reaction.CnH2n+2+nH2O→(2n+1)H2+nCO (endothermic reaction)  [Chemical Formula 2]
Therefore, a partial oxidation reaction and a steam reforming reaction can both be brought about by proper selection of the reforming catalyst. The partial oxidation reaction can be brought about on the pre-stage side of the catalytic reaction chamber, and the heat thereof can be utilized to bring about partial oxidation and steam reformation on the post-stage side of the catalytic reaction chamber.
In view of this, it has been proposed that a hydrogen-rich gas can be obtained by mixing steam and a hydrocarbon fuel to obtain a feed gas, mixing an oxygen-containing gas (such as pure oxygen) with this feed gas, subjecting the mixed gas thus obtained to a partial oxidation reaction on the pre-stage side of a catalyst layer, raising the temperature of the reaction gas to the temperature required for a steam reforming reaction, and mainly bringing about a steam reforming reaction on the post-stage side of the catalyst layer.
This reforming technology is called autothermal reformation, in which a series of reactions (the reactions of Chemical Formulas 1 and 2) occur at the same time.
With this kind of reformation, when a single reaction chamber is used for the catalytic reaction chamber filled with the reforming catalyst, the temperature begins to rise near the inlet of the catalytic reaction chamber, and the temperature rises steadily downstream, reaching the peak temperature. After this, the temperature settles down to an equilibrium temperature that is determined by the inlet temperature, the inlet gas composition, and the reaction pressure.
The technology disclosed in Patent Document 1 is known as this kind of autothermal technology.
With the technology disclosed in Patent Document 1, as discussed in the Claims of the Specification thereof, there is proposed “a hydrogen generating apparatus for generating hydrogen by bringing a raw material containing a hydrocarbon compound, water, and air into contact with a reforming catalyst body, wherein the reforming catalyst body is constituted by two stages, a reforming catalyst containing at least platinum or rhodium is disposed in the pre-stage, a reforming catalyst containing at least ruthenium or rhodium is disposed in the post-stage, and the reforming catalyst in the pre-stage and the reforming catalyst in the post-stage are made up of mutually different elements.
When this proposed constitution is employed, a reaction including steam reformation can be conducted after a partial oxidation reaction is brought about by the reforming catalyst on the pre-stage side and the temperature has reached a specific region.    Patent document 1: JP 2002-121007A (Claims)
In this conventional technique, however, there has been no debate whatsoever about the state of the non-catalyst portion located upstream from the catalytic reaction chamber.
The non-catalyst portion located upstream from the catalytic reaction chamber is called the antechamber in this application; since the reaction that occurs near the inlet of the catalytic reaction chamber is an exothermic reaction, the temperature at this portion can rise quite high. Therefore, the temperature is also quite high at the outlet portion of the antechamber (the portion linked to the inlet into the catalytic reaction chamber). If we here consider the gas that reaches this portion, we see that the gas at this portion is a mixed gas that results from oxygen being mixed into feed gas that is a mixture of steam and a hydrocarbon fuel, and because oxygen and hydrocarbon fuel are contained, there is the potential for self-ignition. If self-ignition should occur at this site, soot will be generated and the gas temperature will be abnormally high, among other problems, which causes the inside of the antechamber to be in an unstable state, and the antechamber and catalytic reaction chamber cannot be kept in a good operating state.
The present invention was conceived in light of the above situation, and it is an object thereof to provide a method for manufacturing a hydrogen-containing gas, with which a hydrogen-containing gas is obtained by means of a partial oxidation reaction and a steam reforming reaction, wherein an antechamber provided on the upstream side of a catalytic reaction chamber is in a stable state, and to provide a manufacturing apparatus that makes use of this method.